Video: Setting the CPC screen with CRTC registers - Learn Z80 Lesson P39
Posted: Tue Apr 23, 2019 3:04 am
by akuyou
CRTC registers define the position and shape of the screen.... they allow us to do crazy things, like resize and hardware scroll the screen... they also allow page flipping - and are generally responsible for the impressive demos the CPC has gained over recent years.
Lets check out the CRTC registers and see what they can do!
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Re: Video: Setting the CPC screen with CRTC registers - Learn Z80 Lesson P39
Posted: Sat Sep 14, 2019 11:10 am
by tricky
Nice intro to vertical rupture, I use it in most of my games on the BBC, so sorry for being slightly of off topic.
For Astro Blaster, I use it in a standard way to get a split screen with scrolling play area and a separate status area.
The other thing I use it for is displaying vertical arcade games in what would be 256x256 but only showing 224x256. This gives the original arcade resolution, whilst still making two consecutive rows of memory &200 apart, which, saves some cycles when drawing. As a bonus, the edges of the screen are clipped, so I can save some complication by not software clipping.
I think that this second use is more expensive on the CPC as I don't think it has the timers to get an interrupt every 16 scan lines.
Re: Video: Setting the CPC screen with CRTC registers - Learn Z80 Lesson P39
Posted: Sat Sep 14, 2019 9:22 pm
by akuyou
Good point on the relevance to the BBC of this topic... I don't have the skill right now on the BBC side to cover this, but I'll be running out of prepared 6502 content soon, so maybe it's something I can start researching.